Change width of horizontal rule

Hi, I've added a horizontal rule underneath one of my subheadings but it's not spanning the entire width of the text box. The text is in a markdown.

Is it possible to correct this?

I've attached an example.

Can you share link to page in screenshot? I can take a look

Hey, yeah here you go!

https://magenta-deer-7f8y.squarespace.com/config/pages

pass:1234

/config is url for site owner

Which page?

Sorry about that, here you go: https://magenta-deer-7f8y.squarespace.com/films/thefamilysecret

Awesome, thanks man! Is there any way to do this site wide?

18 minutes ago, IsaacRiches said:

Awesome, thanks man! Is there any way to do this site wide?

hr {
    width: 100%;
}